1. Field of the Invention
The present invention relates to a driving device of bicycle and, more particularly, to a driving device of a type of bicycle which is driven through reciprocating motion of pedals.
2. Prior Art
It has been a common method of obtaining driving force for bicycle (force with which bicycle is driven) by treading a left and a right pedal designed to rotate in a predetermined circular path. Since the driving force obtained through rotation of pedals varies following a cosine curve, being maximum when the pedal's crank is horizontal, and there is a problem that in the vicinities of the upper and lower dead point the treading force is seldom converted into the driving force, the result being that with such a bicycle the driving force generated is intermittent and the driving efficiency is hence low. In order to overcome this problem, various proposals have been made in which rotary or straight-moving pedals are used to undergo alternate reciprocating motion for their motion to be transmitted to the driving wheel for the bicycle to be driven thereby. This way, the upper or lower dead point of poor driving efficiency can be eliminated with additional feature of driving force being generated continuously. To cite a concrete example, there is disclosed in U.S. Pat. No. 3,891,235 a bicycle driving device comprising each one ratchet wheel device on both sides of the driving wheel which transmits to the wheel rotation in one direction but does not transmit thereto rotation in the opposite direction so that the motion of the left and right pedals of the straight motion type is transmitted via the aforesaid ratchet wheel devices to the driving wheel.
With this driving device, however, while it is possible to run forward with the pedals being treaded or coast with the pedals stopped, no arrangement is made for allowing moving back the bicycle. When the left and right pedals are interlocked to move in the directions opposite to each other, the chains linking the pedal and the driving wheel are bound to move also in the opposite directions to each other and, since the left and right chains are pulled in the same direction via the ratchet wheel devices when attempt is made to reverse the driving wheel to move back the bicycle, it is infeasible to reverse the driving device. This can be advantageous in that the bicycle would not move back on, for instance, an up-slope, but at the same time it is a fatal drawback in maneuverability for it cannot be moved back as it is taken out of or into an warehouse or the like.